Safety is always paramount in an daily
life. Self bondage requires even more attention to detail to
ensure safety. Some bondage release setups have bothered me in
the past and I am constantly seeking a safer and more secure
method to time the release.

This search brought me to this forum and
to study pneumatics. Keys magnetize, temperatures vary, and strings
tangle. Compressed air can provide much more holding power than
an electric magnet, without the concern of electric wires attached
to your bondage setup. Compressed air may provide hundreds of
pounds of pushing or pulling power with a fairly small cylinder.
This force must never push or pull on the restraints or anything
else attached to the body. Safety is my highest priority.

By replacing the electric magnet on the
self-bondage stocks with an air cylinder moving a pin, the holding
power can be increased substantially. Then again, I do not want
to spend $100 on a magnet that may not hold well enough. By using
an industrial air cylinder on each wrist cuff, I have increased
the redundancy to double. The 3/4 inch bore X 1 inch stroke air
cylinders at the local industrial supply company cost me about
$15 a piece. The single acting ,spring loaded return ones are
the cheapest and safest in my opinion. These require air pressure
to continue holding and return back when the air pressure is
gone. Double acting cylinders require air pressure to move in
either direction. The most common failure in industrial applications
is air leaks. This will at least reduce the strength or cause
complete lack of function, depending upon the rate of air loss.
Only in extreme cases under severe conditions will a lack of
imaintenance cause the cylinder to seize up. For bondage applications,
careful inspection and lubrication will ensure this will not
happen. Then again, I will not ever see my cylinders reach over
100,000 cycles while exposed to constant industrial dirt and
grime. My home is cleaner than that.

I have no intention of building the electric
stocks as shown on the main page. My intended application is
in both a wooden cross format and a medical 6 point bed tie down
setup. My wrist restraints are locking medical restraints which
require the other hand to unlock and release. Due to this limit,
I desire a release mechanism that lets go of the restraint instead
of the key. An electric magnet capable of holding is well beyond
my budget. Then again, a magnet requires a metal plate to hold.
This is often heavy, gets warm, and shall never be above my head.
With the cylinder operating a moving pin to catch the tie down
ring on my wrist restraints, the release should be extremely
reliable and only be holding the weight of my restraints. So
far, this sounds safer to me.

By using air pressure to hold, I am hoping
to build a setup with sufficient redundancy to prevent another
scare. With multiple timers controlling multiple electric controlled
air valves, the release should occur at the programmed time.
All air valves will be wired and plumbed to dump the air pressure
when they lose electricity. In the event of a power outage, I
will be instantly released. The electric valves that I chose
have 12 volt coils. This allows me to power the relays from an
exhaustible power source (batteries). The timers will be plugged
into the wall but will only control more relays in line with
the battery power. The air compressor will never be directly
attached to the bondage setup. I desire to use a small portable
air tank to supply the initial pressure, By intentionally installing
a small air leak, the pressure will not last forever as a final
fail safe.

Each of the air components were selected
by air pressure rating to ensure safety. My air compressor shuts
off at 100 PSI. Therefore, anything rated above that in industrial
applications is safe. The valves are rated at 125 PSI. The fittings
are 160 PSI. The hose is 250 PSI (this is the most critical in
an air system). The air cylinders are rated at 300 PSI.

My parts order was at the store today!
Both air valves and air cylinders are in my possession and tested.
The function is good, but the air cylinders are noisy in operation.
The finished product will be cushioned with rubber grommets to
reduce noise.

The following images are the actual parts
that will be used.

This is the electric air valves (solenoid
air valves). The pair are bolted together and connected to a
compressed air supply. The upper connection is normally closed
and the lower one is normally open. The brass item installed
in the lower port is an air exhaust muffler.

Now comes the fun part, building the brackets
to hold the air cylinder and sliding pin.